The present invention relates to the field of robotics. More particularly, the present invention relates to biologically-inspired, multi-segmented robots.
In general, robots are electromechanical devices which are designed to perform one or more specific tasks that may be too complex, too difficult or too dangerous for humans. Robots have been used, and will continue to be used in numerous and diverse applications including biomedical applications, household or domestic applications, industrial applications, space and/or hazardous environment exploration applications, educational applications, toys, entertainment and many others.
While virtually all robots engage in some degree of movement, some robots may be described as fixed, while others may be described as mobile. Mobile robots are capable of moving or propelling themselves from one location to another location. Presumably, the ability to move from one location to another is essential for accomplishing the one or more tasks for which they are designed.
As one might expect, mobility may be achieved in any number of ways. For instance, some robots are designed with wheels. Other robots use tracks. Still others employ animal or human-like limbs (e.g., legs). FIG. 1 is a flow diagram that illustrates a conventional approach to mobility control for robots that fall into this latter category. As shown, mobility is achieved through a controller, which sends control commands or signals to an actuator, such as a metal piston or an electric motor. The actuator then drives a joint associated with a corresponding limb. If the limb comprises multiple joints, then multiple motors are also required, where each joint is independently driven by its own dedicated motor. FIG. 1 also indicates that conventional designs generally employ sensors, such as position encoders, as part of a sensor feedback loop, where the controller receives information from a corresponding sensor, and wherein the motor responds by actuating the corresponding joint accordingly. In conventional designs, the sensor feedback loop is the only mechanism that provides control and stability to the system. Conventional designs, as illustrated in FIG. 1, tend to be inefficient, slow, heavy, inflexible, and they depend on extremely complex, mathematically intensive control algorithms and computer-based control techniques.
A more specific example of a conventional, legged robot is described in a series of patents relating to U.S. Pat. No. 5,936,367. The robot described in these patents comprises two legs. Each leg, in turn, comprises six joints, where each joint is independently actuated by a corresponding electric motor. Such a robot could easily weigh 300 pounds, due to a large extent on the relatively heavy electric motors that generate the torque needed to actuate the joints.
As one skilled in the art will readily appreciate, a great deal of control is required to properly operate the electric motors needed to coordinate mobility in the conventional legged robot design described in U.S. Pat. No. 5,936,367. Generally, a sophisticated computer (e.g., a Sparc computer) is needed to perform the complex, brute-force computations which are necessary in order to achieve the required level of control. While these conventional designs generally work well in highly structured situations, where the environment does not significantly vary with respect to the models upon which the computer is programmed, these designs have serious limitations when used in unstructured environments.
Accordingly, there is a strong demand to develop biologically inspired robots, as an alternative to conventional robot designs which employ mathematical modeling and computationally intensive techniques to achieve mobility. In biologically inspired systems, nature""s efficient solutions for controlling complex movements are integrated into the robot design, where artificial muscles, rather than pistons or electric motors, are typically used to control motion. Biologically inspired designs offer a faster, more efficient, flexible and versatile approach. However, a simple, intelligent mobility control technique for coordinating the various artificial muscles of a biologically inspired robot design is still needed.
The present invention involves biologically inspired, multi-joint, multi-segmented robots. More specifically, the present invention involves a logical, intelligent technique that does not rely on mathematical modeling or computationally intensive techniques to control the mobility of a biologically inspired, multi-joint, multi-legged robot. As such, the present invention relies upon certain artificial, anatomical and neuro-physiological features that are similar to features found in actual biological systems. For instance, the present invention employs muscle-like actuators. Each muscle-like actuator comprises an artificial muscle, or contractile portion, and an artificial tendon portion. The artificial tendons and artificial muscles resemble, both in form and function, their biological counterparts, such that they operate either actively or passively to provide xe2x80x9cintelligent, spring-likexe2x80x9d properties.
The present invention also takes advantage of the built-in, mechanical constraints that are associated with the aforementioned anatomical and neuro-physiological features. For example, each artificial tendon and artificial muscle is designed in accordance with a pre-selected operational range, which determines the force-length and force-velocity characteristics of the artificial tendons and muscles. In another example, the joints, such as the knee, are designed to be self-limiting, much like the human knee. Together, the utilization of artificial, anatomical and neuro-physiological features, and the mechanical constraints that are associated with these features provide mechanical feedback that is similar to the type of feedback that is inherent in genuine biological systems. This mechanical feedback helps to simplify the process of controlling the mobility of the multijoint robot.
In accordance with exemplary embodiments of the present invention, the muscle-like actuators are organized into functional muscle groups. Activation of the muscle-like actuators in functional muscle groups provides the necessary force and position control that is needed to achieve tasks such as walking, bending and grasping. Controlling the activation of the various muscle groupings is, in turn, controlled by a sequence of discrete xe2x80x9cif-thenxe2x80x9d, or xe2x80x9cfuzzy if-thenxe2x80x9d logical rules, which may be optimized over time through reinforcement learning.
In view of that which is stated above, it is an objective of the present invention to provide a biologically inspired, multi-legged robot that employs anatomical and neuro-physiological features which exhibits self-limiting, mechanical constraints similar to those found in genuine biological systems.
It is another objective of the present invention to provide stable, efficient and natural mobility control through the use of muscle-like actuators rather than pistons or electric motors.
It is yet another objective of the present invention to provide mobility control for a multi-joint, multi-legged robot through the use of monoarticular and biarticular muscle-like actuators.
It is still another objective of the present invention to provide sensory feedback, to optimize the activation of the muscle-like actuators.
It is another objective of the present invention to provide the force and position control needed for mobility by activating, in tandem with each other, different functional muscle-like actuator groupings.
It is another objective of the present invention to provide stiffness control without the loss of energy that occurs with activation of two one-joint, antagonist muscle-like actuators, by simultaneously activating monoarticular and biarticular, antagonist, muscle-like actuators.
It is another objective of the present invention to provide a logical mobility control technique by employing performance based control, rather than control over each individual joint.
It is another objective of the present invention to provide control over the various functional muscle-like actuator groupings through the use of xe2x80x9cif-thenxe2x80x9d or xe2x80x9cfuzzy if-thenxe2x80x9d rules.
It is another objective of the present invention to provide reinforcement learning techniques to adjust the timing of the functional muscle-like actuator groupings, thereby optimizing mobility.
In accordance with a first aspect of the present invention, the above-identified and other objectives are achieved by a robot that includes a first anatomical segment, a second anatomical segment, and a joint which is attached to the first anatomical segment, where the first anatomical segment moves relative to the second anatomical segment as a function of an amount of rotation associated with the joint. The robot also includes a muscle-like actuator having a first end fixed to a position along the first anatomical segment and a second end fixed to a position along the second anatomical segment. The muscle-like actuator also has a predefined control operating range, such that when the muscle-like actuator is activated it undergoes a predefined change in length, which causes the joint to rotate by a corresponding, predefined amount that is a function of the predefined change in length and the positions along the first and second anatomical segments.
In accordance with another aspect of the present invention, the above-identified and other objectives are achieved by a robot that includes a plurality of anatomical segments and a plurality of joints, where each of the joints couples two adjacent anatomical segments such that the two adjacent anatomical segments move relative to each other as a function of an amount of rotation associated with the joint. The robot also includes a plurality of muscle-like actuators, each comprising a first end fixed to a position along one of the plurality of anatomical segments and a second end fixed to a position along a second one of the plurality of anatomical segments, where activation of a muscle-like actuator causes torque to be applied to at least one of the plurality of joints, thereby causing two or more of the anatomical segments to move relative to each other. In addition, the robot includes a controller which is coupled to each of the plurality of muscle-like actuators. The controller includes means for defining each of a plurality of states, where each of the plurality of states corresponds with a different functional grouping of muscle-like actuators, and where, for a given state, the muscle-like actuators associated with the corresponding functional grouping are defined as being activated and the muscle-like actuators that are not associated with the functional grouping are defined as being deactived.
In accordance with yet another aspect of the present invention, the above-identified and other objectives are achieved by a biologically-inspired, multi-segmented robot. The robot includes a plurality of anatomical segments and a plurality of joints, where each of the plurality of joints couples two adjacent anatomical segments. The robot also includes a plurality of muscle-like actuators, where each of said muscle-like actuators includes a first and a second end, wherein the first end of each muscle-like actuator is attached to one of the plurality of anatomical segments, where the second end of each muscle-like actuator is attached to a second one of the plurality of anatomical segments, and where the plurality of muscle-like actuators and joints are configured so as to provide mechanical feedback for the muscle-like actuators. The robot further includes a controller, which activates one or more functional groupings of the muscle-like actuators to achieve a desired mobility event, and one or more sensors coupled to the controller and the anatomical segments, where the sensors provide feedback data to the controller, and where the feedback data defines a position associated with one or more of the anatomical segments.
In accordance with still another aspect of the present invention, the above-identified and other objectives are achieved through a method for controlling mobility in a biologically-inspired, multi-joint, multi-segmented robot. The method involves activating a first functional grouping of muscle-like actuators, which causes a repositioning of one or more of the multiple segments associated with the robot, so as to achieve a first mobility event. The method also involves measuring a status of the robot, and based thereon, determining whether the first mobility event has been achieved. The method then involves activating a second functional muscle grouping of muscle-like actuators, if it is determined that the first mobility event has been achieved, where the activation of the second functional muscle grouping causes a further repositioning of one or more of the multiple segments associated with the robot, so as to achieve a second mobility event.
In accordance with another aspect of the present invention, the above-identified and other objectives are achieved through a method for controlling mobility in a biologically-inspired, multi-joint, multi-segmented robot. The method involves quantifying a state of said robot and activating a first functional grouping of muscle-like actuators, to achieve a first desired mobility event, in accordance with a level of activation selected from a set of activation levels which includes at least one intermediate activation level. The first functional grouping of muscle-like actuators comprises a subset of all muscle-like actuators associated with the robot. The method also involves actuating one or more segments associated with the robot based on the activation of the first functional grouping of muscle-like actuators.